Water levels in the Great Lakes fluctuate naturally through the year. Here’s why that matters:

The cycle of high and low water levels in the Great Lakes matters to the whole country. Why?

Glad you asked! When the water level in the Great Lakes fluctuates, it affects everyone differently—from commercial shippers carrying heavy loads, to lakefront property owners concerned about erosion.

Keith Kompoltowicz, chief of hydrology for the Detroit Corp of Engineers, says the water level in the lakes varies frequently.

“The lakes fluctuate anywhere from one foot to 16 inches or so, on average, over the course of the year,” he explains.

Snow, rain, and runoff cause the lake levels to rise through the spring and early summer, peaking in July. In summer, drier conditions and evaporation cause the water level to drop until mid-winter. And then, just like the seasons, the cycle begins again.

Because the Great Lakes are a shipping hub, these changing water levels can have a rippling effect throughout the country.